This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-072701, filed Mar. 17, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of forming projecting electrodes and a method of manufacturing a semiconductor device provided with projecting electrodes.
In a semiconductor device called, for example, GBA (ball grid array), a semiconductor circuit consisting of an LSI, etc. is mounted on an interposer and solder balls (projecting electrodes) are arranged to form a matrix on the lower surface of the interposer. FIGS. 31 to 35 are cross sectional views collectively exemplifying the conventional method of manufacturing a semiconductor device of this type. As shown in FIG. 31, an interposer 1 consists of a film substrate somewhat larger than the planar size of a semiconductor circuit 5. Mounted on one surface of the interposer 1 are a plurality of first connection pads 2 and a plurality of second connection pads 3 arranged to form a matrix and connected, respectively, to the first connection pads 2 via connection wirings (not shown). The interposer 1 is provided with a plurality of open portions 4 arranged to conform with the second connection pads 3 and extending through the interposer 1 in its thickness direction. The plural first connection pads 2 are connected to the semiconductor circuit 5 via a plurality of bump electrodes 4, respectively. Also, the semiconductor circuit 5 is covered with a resin sealing film 6. As shown in FIG. 32, a metal mask 7 having a plurality of open portions 8 arranged to form a matrix and conforming with the plural open portions 4, respectively, is disposed on the interposer 1 to align the open portions 8 and 4. The open portion 8 is equal to the open portion 4 made in the interposer 1 in the shape and size in the planar direction. Then, the surface of the structure is coated with a conductive paste 9 consisting of a semi-molten solder paste to fill the open portions 4 and 8. The metal mask 7 is made of a metal low in its adhesivity to the conductive paste 9. However, since it is possible for the metal mask 7 to be bonded to the solidified solder after the conductive paste 9 is solidified, the metal mask 7 is removed while the conductive paste 9 is in a molten state, as shown in FIG. 33. Then, the plural conductive pastes 9 are solidified by a reflow treatment to form a plurality of solder bumps 10, as shown in FIG. 34. It follows that the solder bumps 10 are arranged to form a matrix, as shown in FIG. 35.
In the conventional semiconductor device of this type, a flux coating tool or the metal mask 7 of the structure conforming with the arrangement of the open portions 4 of the interposer 1 is used in the coating step of the conductive paste 9. This gives rise to the problem that, if the arrangement of the open portions 4 is changed in accordance with the design of the semiconductor circuit 5, etc., it is necessary to use a flux coating tool or the metal mask 7 conforming with the arrangement of the open portions 4. It should also be noted that the height of the projecting portion of the solder bump 10 from the interposer 1 should desirably be at least 0.2 mm in view of the bonding capability of the solder bump 10 to the external circuit. If the metal mask 7 is made thicker for ensuring a sufficient height of the projecting portion of the solder bump 10, however, the contact area between the open portion 8 of the metal mask 7 and the conductive paste 9 filling the open portion 8 is increased, giving rise to serious problems. For example, it is possible for a part or the entire portion of the conductive paste 9 positioned within the open portion 8 to be pulled up when the metal mask 7 is pulled up. Alternatively, the conductive paste 9 is likely to be deformed by a slight impact or the like given to the paste 9 after the metal mask 7 is detached from the conductive paste 9. It may be possible to prevent the deformation by decreasing the ratio of the solvent contained in the conductive paste. In this case, however, the bonding strength between the conductive paste 9 and the metal mask 7 is increased, with the result that the a part or the entire portion of the conductive paste 9 within the open portion 8 is likely to be pulled up when the metal mask 7 is pulled up. It follows that it is difficult to form the solder bumps 10 having a sufficient height and a uniform shape by using the metal mask 7. What should also be noted is that, if the conductive paste attached to the open portion 8 of the metal mask 7 is solidified as it is, the open portion is diminished so as to make it impossible to use again the metal mask 7. It follows that it is necessary to wash the metal mask 7 to remove the conductive paste attached thereto every time the printing is performed by using the metal mask 7 or after the printing is performed only a few times, leading to a low productivity.
An object of the present invention is to form satisfactory projecting electrodes on a substrate with a high productivity.
According to a first aspect of the present invention, there is provided a method of forming projecting electrodes, comprising forming a plurality of holes through a laminate structure including a first film having a plurality of electrodes arranged on one surface thereof and a second film attached to the other surface of the first film, the plurality of holes conforming with the plurality of electrodes; loading a conductive paste in the plural holes; hardening the conductive paste to form the projecting electrodes; and peeling the second film from the first film with the projecting electrodes left mounted on the first film.
In the method of the present invention for forming projecting electrodes, the conductive paste loaded in the holes extending through the laminate structure including the first film and the second film is hardened, followed by peeling the second film off the first film. Naturally, it is impossible for the entire region forming the projecting electrode of the conductive paste to be exposed to the outside in a non-hardened state. It follows that the projecting electrode is not deformed when the second film is peeled off the first film. It should also be noted that, since the second film can be set at an optional thickness, the projecting electrode formed within the hole in the second film can be allowed to project from the first film in a desired height. What should also be noted is that, if the conductive paste is loaded in the hole by a screen printing method using the second film as a printing mask, the projecting electrode consisting of, for example, a solder can be formed on the first film without fail without using an exclusive printing mask.
According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device provided with projecting electrodes, comprising forming a plurality of holes through a laminate structure including a first film having a plurality of first electrode terminals and a plurality of second electrode terminals connected respectively to the plurality of first electrode terminals, the first and second electrode terminals being arranged on one surface the first film, and a second film attached the other surface of the first film, the plurality of holes conforming, respectively, with the plurality of second electrode terminals; connecting a plurality of electrode terminals of a semiconductor circuit to the plurality of first electrodes, respectively; loading a conductive paste in the plurality of holes conforming with the plurality of second electrode terminals; hardening the conductive paste to form the projecting electrodes; and peeling the second film from the first film with the projecting electrodes left mounted on the first film.
The particular method of the present invention makes it possible to connect easily the semiconductor circuit to the projecting electrodes having a sufficient height.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.